debugcommands: introduce debugpeer command

`hg debugpeer <path>` will establish a connection to a peer repository
and print information about it.

If you add --debug, it will log low-level protocol request info. This
will be useful for upcoming tests around protocol handshaking.

Differential Revision: https://phab.mercurial-scm.org/D2025

mercurial/debugcommands.py

@@ -1693,6 +1693,25 b' def debugpathcomplete(ui, repo, *specs, '
     ui.write('\n'.join(repo.pathto(p, cwd) for p in sorted(files)))
     ui.write('\n')
 
+@command('debugpeer', [], _('PATH'), norepo=True)
+def debugpeer(ui, path):
+    """establish a connection to a peer repository"""
+    # Always enable peer request logging. Requires --debug to display
+    # though.
+    overrides = {
+        ('devel', 'debug.peer-request'): True,
+    }
+
+    with ui.configoverride(overrides):
+        peer = hg.peer(ui, {}, path)
+
+        local = peer.local() is not None
+        canpush = peer.canpush()
+
+        ui.write(_('url: %s\n') % peer.url())
+        ui.write(_('local: %s\n') % (_('yes') if local else _('no')))
+        ui.write(_('pushable: %s\n') % (_('yes') if canpush else _('no')))
+
 @command('debugpickmergetool',
         [('r', 'rev', '', _('check for files in this revision'), _('REV')),
          ('', 'changedelete', None, _('emulate merging change and delete')),

tests/test-completion.t

@@ -102,6 +102,7 b' Show debug commands if there are no othe'
   debugnamecomplete
   debugobsolete
   debugpathcomplete
+  debugpeer
   debugpickmergetool
   debugpushkey
   debugpvec
@@ -281,6 +282,7 b' Show all commands + options'
   debugnamecomplete: 
   debugobsolete: flags, record-parents, rev, exclusive, index, delete, date, user, template
   debugpathcomplete: full, normal, added, removed
+  debugpeer: 
   debugpickmergetool: rev, changedelete, include, exclude, tool
   debugpushkey: 
   debugpvec: 

tests/test-debugcommands.t

@@ -381,3 +381,24 b' Test debugcapabilities command:'
       https
     stream
       v2
+
+Test debugpeer
+
+  $ hg --config ui.ssh="\"$PYTHON\" \"$TESTDIR/dummyssh\"" debugpeer ssh://user@dummy/debugrevlog
+  url: ssh://user@dummy/debugrevlog
+  local: no
+  pushable: yes
+
+  $ hg --config ui.ssh="\"$PYTHON\" \"$TESTDIR/dummyssh\"" --debug debugpeer ssh://user@dummy/debugrevlog
+  running "*" "*/tests/dummyssh" 'user@dummy' 'hg -R debugrevlog serve --stdio' (glob)
+  devel-peer-request: hello
+  sending hello command
+  devel-peer-request: between
+  devel-peer-request:   pairs: 81 bytes
+  sending between command
+  remote: 384
+  remote: capabilities: lookup changegroupsubset branchmap pushkey known getbundle unbundlehash batch streamreqs=generaldelta,revlogv1 $USUAL_BUNDLE2_CAPS_SERVER$ unbundle=HG10GZ,HG10BZ,HG10UN
+  remote: 1
+  url: ssh://user@dummy/debugrevlog
+  local: no
+  pushable: yes

tests/test-help.t

@@ -948,6 +948,7 b' Test list of internal help commands'
    debugoptEXP   (no help text available)
    debugpathcomplete
                  complete part or all of a tracked path
+   debugpeer     establish a connection to a peer repository
    debugpickmergetool
                  examine which merge tool is chosen for specified file
    debugpushkey  access the pushkey key/value protocol